Winterizing Your Crawl Space

Winterizing your crawl space is a must have if your home resides anywhere temperatures fall below 32 degrees. The crawl space winterization package is exclusively offered by Crawl Space Ninja to ensure your crawl space is performing at peak efficiency.

The winterization of your crawl space will help by offering the best available comfort for your home as well.  Best of all this package is designed to be installed on any crawl space whether it is currently encapsulated or vented.

What is Crawl Space Winterization?

To winterize means to prepare or equip for winter weather. Many crawl spaces across America are not prepared for the cold weather coming this winter. Pipes will freeze and water damage restoration companies will be called out to address flooding issues. All because homeowners fail to recognize the importance of preparing your crawl space and your home for the winter that is coming.

Crawl space winterization is simply installing proper insulation and air sealing where it is needed most. The crawl space has many components from foundation walls to rim joists to subfloors. Most if not all of the areas are not insulated much less insulated and air sealed. Proper winterization can help keep your crawl space close to a constant temperature year round.

How Does Weatherizing the Crawl Space Help My Home?

Winterizing, also know as weatherizing, the crawl space has a significant affect on the comfort of your home. Up to 50% of the crawl space air can migrate to the living space. The stack effect describes how air moves into the home around the foundation and exits through the attic. This air movement means that cold crawl space air can easily enter your living space. Minimizing cold drafts while watching your favorite television show or reading to your children can be accomplished with proper air sealing in the crawl space.

Many crawl space contractors refuse to insulate the crawl space and say it is not necessary. This is not the same opinion held by Crawl Space Ninja or the Department of Energy. says the crawl space is one of the top areas of the home that should be properly insulated. Our approach takes it a step further. The way we perform air sealing and insulating follows the guidelines set by the engineers at

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What are the Key Crawl Space Areas to Insulate and Air Seal

Crawl Space Ninja has identified several key components to proper winterization. This includes the vents, the foundation wall, the rim joists and the subfloor. Performing weatherization in these areas may require additional items to control humidity and address soil gases.

Crawl Space Vents Need to be Sealed

Sealing and insulating the crawl space vents will keep cold air out in the winter. It will also keep warm humid air out in the summer. Sealing the vents alone will not control humidity. It will also not keep the crawl space warm in the winter by itself. But insulating and air sealing crawl space vents has a major impact on protecting the crawl space from the elements.

Foundation Wall Insulation

Foundation walls are directly exposed to the outside air temperatures. Cold temperatures easily transfer energy that lowers the crawl space temperature through the foundation walls. Many exterior crawl space walls are not insulated on the inside or outside. Even less are air sealed. Not all foundation walls require insulation. But many homes are built with plumbing and HVAC components penetrating the exterior walls of the crawl space. Air sealing those large gaps are vital to stopping cold outside air. Installing foamboard or other types of foundation wall insulation will help keep cold energy from transferring into the crawl space.

Subfloor Insulation

Vented crawl spaces require subfloor insulation. Sealed crawl spaces do not therefore foundation wall insulation can replace subfloor insulation. There is no need to remove subfloor insulation if it exists in your crawl space unless it has been compromised. Mold and moisture are damaging to subfloor insulation. If mold or moisture are present, it is recommended to remove and dispose subfloor insulation.

According to, subfloor insulation can be added back when sealing the crawl space. But foundation wall insulation can replace the need for subfloor insulation. The crucial component to ensuring the subfloor is properly winterized is air sealing. Air sealing the subfloor is crucial whether the crawl space has subfloor insulation or not. Air sealing major gaps in the floor between the crawl space and living space will greatly reduce drafts. According to, reducing drafts in the home will cause the thermostat to kick on less often and improve comfort.

Rim Joist Insulation

According to, rim joist insulation is recognized as a “critical seal. The rim joist is the wood cavity that sits above the exterior foundation wall. This area of wood is susceptible to condensation due to its direct proximity to the cold and heat of the outside. Installing rim joist insulation is required by many local codes enforcement agencies. However, air sealing rim joists is usually not required. Given the engineers at highly recommend it, so do I. Insulating and air sealing rim joists can prevent air movement up exterior walls. It can also prevent mold and wood rot fungus from condensation.

Properly winterizing the crawl space may save you money. That is important but in my opinion not why you should do it. Properly winterizing the crawl space can make your home more comfortable and potentially improve your indoor air quality. Protecting my family from poor indoor air quality far outweighs any potential monetary benefit of winterizing. Contact Crawl Space Ninja today to learn more how we can help improve your crawl space

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Please contact us to schedule your assessment to fix your crawl space, basement issue. 


Do you need help with mold removal, crawl space encapsulation, crawl space insulation, vapor barrier, waterproofing, foundation repair, basement waterproofing, or controlling humidity in your crawl space?

If you live in Georgia, Delaware, North Carolina, South Carolina, Tennessee, or Kentucky, Crawl Space Ninja can help!


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2 thoughts on “Winterizing Your Crawl Space”

  1. I live in Southern California and my 1952 house has a vented crawl space. What is the correct way to insulate and should I also encapsulate? Who do you hire that is verifiably qualified to do this kind of work?

    1. Hi Steffanie, Here is a video on 6 places to insulate if you leave your crawl space vented. Crawl space encapsulation could be a better option if your crawl space is damp or has high humidity. In that case you could insulate the crawl space differently. Have you seen the Essential Guide to Crawls Space Encapsulation Video? It helps explain insulation for an encapsulated crawl space. One last video I recommend is how to choose a crawl space contractor, we do not have anyone in your area we could recommend, sorry. This is a 3 part series, I hope this information helps you.

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